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Biomedical subjects

B Champagne

Publications and source records attributed to B Champagne.

9 recordsLinked to original sources
PubMed2001

Tracking oligodendrocytes during development and regeneration.

Over the past decade, advances in strategies to tag cells have opened new avenues for examining the development of myelin-forming glial cells and for monitoring transplanted cells in animal models of myelin insufficiency. The strategies for labelling glial cells have encompassed a range of genetic modifications as well as methods for directly attaching labels to cells. Genetically modified oligodendrocytes have been engineered to express enzymatic (e.g., beta-galactosidase, alkaline phosphatase), naturally fluorescent (e.g., green fluorescent protein), and antibiotic resistance (e.g., neomycin, zeomycin) reporters. Genes have been introduced in vivo and in vitro with viral or plasmid vectors to somatically label glial cells. To generate germ-line transmission of tagged oligodendrocytes, transgenic mice have been created both by direct injection into mouse fertilized eggs and by "knock-in" of reporters targetted to myelin gene loci in embryonic stem cells. Each experimental approach has advantages and limitations that need to be considered for individual applications. The availability of tagged glial cells has expanded our basic understanding of how oligodendrocytes are specified from stem cells and should continue to fill in the gaps in our understanding of how oligodendrocytes differentiate, myelinate, and maintain their myelin sheaths. Moreover, the ability to select oligodendrocytes by virtue of their acquired antibiotic resistance has provided an important new tool for isolating and purifying oligodendrocytes. Tagged glial cells have also been invaluable in evaluating cell transplant therapies in the nervous system. The tracking technologies that have driven these advances in glial cell biology are continuing to evolve and present new opportunities for examining oligodendrocytes in living systems. Microsc. Res. Tech. 52:766-777, 2001. Published 2001 Wiley-Liss, Inc.

Animals↗
PubMed2000

Three-wave mixing in chiral liquids

Second-order nonlinear optical frequency conversion in isotropic systems is only dipole allowed for sum- and difference-frequency generation in chiral media. We develop a single-center chiral model of the three-wave mixing (sum-frequency generation) nonlinearity and estimate its magnitude. We also report results from ab initio calculations and from three- and four-wave mixing experiments in support of the theoretical estimates. We show that the second-order susceptibility in chiral liquids is much smaller than previously thought.

Journal Article↗
PubMed1998

Proteolytic cleavage of ICAM-1 by human neutrophil elastase.

Human leukocyte elastase (HLE) participates in tissue destruction in a number of inflammatory disorders, including rheumatoid arthritis and cystic fibrosis. Since HLE has been shown to bind to Mac-1, and ICAM-1 plays a key role during the recruitment and the activation of leukocytes at inflamed sites, we investigated the capacity of HLE to cleave ICAM-1. Flow-cytometric analyses showed a dose-dependent cleavage of ICAM-1 by HLE on different human cell lines. The cleavage was completely inhibited by alpha1-antitrypsin, a natural HLE protease inhibitor. The ability of HLE to degrade ICAM-1 was further confirmed by electrophoretic analysis using a soluble form of ICAM-1 (D1-D5). Enzymatic removal of N-linked glycosylation did not significantly modulate ICAM-1 cleavage by HLE, while removal of sialic acid residues partially reduced the sensitivity of ICAM-1 to HLE. We further showed that sputum of cystic fibrosis patients contains high levels of HLE activity capable of cleavage of cell surface ICAM-1. The cleavage induced by incubation of cells with the sputum sample was totally inhibited by alpha1-antitrypsin and the specific peptidic HLE inhibitor N-methoxysuccinyl-Ala-Ala-Pro-Val-chloromethylketone. Moreover, the cleavage of ICAM-1 was concomitant to that of CD4 at the surface of the same cell, at the same amplitude, and at all HLE concentrations. The capacity of HLE to modulate the expression of ICAM-1 on the surface of leukocytes by proteolytic cleavage brings support to the hypothesis that overproduction of HLE can cause severe immunologic lung disorders by affecting intercellular adhesion.

Adolescent↗
PubMed1995

The mammalian RPS6 gene, homolog of the Drosophila air8 tumor suppressor gene: is it an oncosuppressor gene?

The mammalian gene encoding the S6 ribosomal protein is the homolog of the Drosophila air8 tumor suppressor gene. We assigned the rat Rps6 gene to chromosome 5q22-33. The rat 5q22-33 chromosome region, previously shown to bear a malignant transformation suppressor gene, is homologous to the human 9p2l region, frequently deleted in various kinds of cancers and also containing at least one tumor suppressor (oncosuppressor) gene. To test the possibility that the Rps6 gene could be an oncosuppressor gene in mammals, we analysed its sequence and expression in normal and malignantly transformed cells. In mouse hepatoma cells (BWTG3), the Rps6 gene is hemizygously deleted but the remaining copy shows no sequence anomaly in the coding region, indicating that Rps6 is not oncosuppressor and that another gene acting as an oncosuppressor is located in its vicinity. In human tumor cells, the RPS6 gene is retained in cells showing deletion of the near-by gene, IFNB. Our results do not support the possibility that the RPS6 gene acts as an oncosuppressor gene in mammalian cells.

Animals↗
PubMed1990

Adherence of HDPE powder coating on Co-Cr surfaces: effect of substrate preparation and gas sterilization.

As part of the development of a hemiarthroplasty implant with a compliant surface layer, the effect of surface preparation of a cast Co-Cr alloy substrate on the adhesion of a polymeric coating was studied. High-density polyethylene (HDPE) coatings were deposited on Co-Cr alloys without adhesive by spraying powder onto the surface of specimens maintained at a controlled temperature. Prior to deposition, two different types of surface preparation were carried out: chemical etching and grit-blasting. Adherence tests were performed in order to study the effect of the surface preparation of a Co-Cr alloy on the adherence of the HDPE film. The etching process enhanced the adherence by a factor of 10 compared to the grit-blasting process. For coatings deposited on grit-blasted Co-Cr surfaces, rupture occurred at the interface (adhesive mode) as well as in the coating (cohesive mode). A full cohesive mode was observed for films deposited on etched surfaces. Gas sterilization with an ethylene oxide and Freon 12 solution did not change significantly the adherence of the film deposited on etched surfaces. Examination of the surfaces indicated that the etching process created a specific type of porosity consisting of dendritic cavities whereas grit-blasting produced surface irregularities. Cavities produced by etching were larger that the polymer powder particles and could be easily filled. The coating of an etched Co-Cr alloy substrate with a layer of HDPE provided an interface that could probably sustain the physiological loading in a normal synovial joint.

Biocompatible Materials↗